As Animationnodes is somewhat hard to understand for, and explain to, new users i would advise not to buy if you feel that this topic (Animationnodes) is over your head. I will likely not be able to help you if you encounter problems as there may be loads of rootcauses for your individual problem.
Please make sure, that you update vc_redist.x64.exe on your windows-machine to make Animationnodes work properly
When importing the tree into a new scene you have to press T in the animationnodes-node-editor to open the side panel. in there you have to select the scene the lightning-tree will work upon.
There is a masternode where all the different parameters feed into.
Iteration: how many ligthning Bolts
Lightning Length: How many points the Main Lightning will have
Sec Amount: how many Lightning Bolts will offspring from the main
Sec Length Min: How many points the Sec Lightning will have minimum
Sec Length Max: How many points the Sec Lightning will have maximum
Add Random: Add Random
Wiggle Speed: The points of all ligthning Parts will wiggle based on this
Wiggle Amount: The points of all ligthning Parts will wiggle in there Range based on this
Arch Min: Change overall Ligthning lenght
Arch Max: Change overall Ligthning lenght
Curl Primary: How much the primary Bolt will curl (combined with "Iteration" set to 2 or more there migth be nice effects)
Curl Secondary: How much the secondary Bolts will curl
Duration Fade: Fading out of the main Bolt
Scale: It is in there because it is in there - using it might give different results
Thick Main: Thickness of main bolt
Thick Sec: Thickness of secondary bolts